The present invention relates to an overload clutch and, more particularly, to an overload clutch for a rotating agitation member in a cleaning machine such as a surface cleaning machine.
Many surface cleaning machines such as electric vacuum cleaners include a rotating agitation member to improve debris pick-up by a nozzle. The rotating agitation member is driven by a separate motor or the vacuum motor either directly or via a suitable drive such as a belt drive. The rotating agitation member may get stuck, and the motor driving the rotating agitation member will be damaged due to frictional heat if power transmission from the motor to the rotating agitation member is not cut off.
Overload disconnection devices provide solutions for cutting off power transmission from a driving part to a driven part when overload occurs. Some designs use magnetically controlled torque limiting clutches, and an example of which includes a motor driven hub carrying two concentric cup-shaped rings with a cylindrical permanent magnet therebetween. Keeper plates are pivotally secured to the hub and overlay coplanar edges of the rings to which the keeper plates are magnetically attracted. The hub has an extension on which freely rotates a power output disc provided with projecting fingers that engage with the keeper plates when they are in radial positions with respect to the hub. When an overload is applied to the output disc, the fingers turn the keeper plates until they are disengaged from the disc. Thus, the power output disc and hub are released to turn freely independent of each other, without generating frictional heat therebetween. However, resetting of the torque limiter clutch after it has disconnected the overload requires manually turning the keeper plates back to radially extending positions and starting the motor again to reestablish the normal drive-through conditions.
Another type of overload clutch design includes a drive element and a driven element which are arranged concentrically to one another, thereby forming an intermediate space for accommodating a plurality of steel balls. A star-shape collar and a torsion spring are utilized to retain the steel balls in their respective positions in the intermediate space during normal operation. The steel balls are moved into their respective recesses when an overload occurs. The steel balls must be received in a sealed space to prevent them from being lost. Furthermore, the structure and assembly of the overload clutch of this type are complicated and result in high cost for troublesome processing and assembling of the complicated structures of the star-shaped collar and other elements.
The present invention is intended to provide an overload clutch that has synergistic application to rotating agitation members of surface cleaning machines and that is simple in structure to allow manufacturing and easy assembly at low cost.